Cursive character generator



Dec. 17,1968 F. K.STAUFFERY 3,417,281

CURS IVE CHARACTER GENERATOR Filed Nov. 19, 1965 I s Sheets-Sheet 1 4 F/6. 1 F/G. 2

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o 4 e12|62o242832364o TIME 60 62 63 H6 4 m a UNBLANKED TIME 7 lA/VE/VTURFRANKLIN KSMUFFER 5r WMWM ATTORNEY United States Patent 0 3,417,281CURSIVE CHARACTER GENERATOR Franklin K. Staulfer, Sudbury, Mass.,assignor to Raytheon Company, Lexington, Mass., a corporation ofDelaware Filed Nov. 19, 1963, Ser. No. 324,707 16 Claims. (Cl. 315-18)This invention relates to the'generation and visual display ofelectrical signals and more particularly to improved means for tracing adesired form or character upon the face of a cathode ray device.

The generation of characters for display on a cathod ray tube has beenaccomplished in numerous ways. Among these is the formation of theelectron beam in the cathode ray tube such that the cross-sectional viewof the beam becomes the outline of the character. For example, acharacter may be formed by individually gating strokes or dots from aformat of straight lines or dots, respectively. However, the outline ofcharacters formed in this manner frequently only approximates thegeneral outline of the original character and usually lacks thedefinition and ease of identification of a well-defined character, suchas might be manually drawn. When an attempt is made to provide acharacter with the aforementioned definition, it generally requiresnumerous electric-a1 circuits which adds to the over-all cost andcomplexity of the system. For example, one method is to generate x and ytime functions of the desired character and then make a Fourier waveformanalysis of each function in order to generate and sum the necessarysine and cosine frequency components prior to application to theappropriate x and y inputs to the cathode ray tube. For a reasonableapproximation to the functions, approximately ten sine and cosine termsare required, having both positive and negative terms. This arrangementis difficult to provide, and results in extensive circuitry whichincreases both operational and construction costs. Another known systemdisplays characters by dividing the characters to be displayed into anumber of straight line increments which are then successively assembledin proper sequence into a complete character. The straight lineincrements are traced or drawn on the cathode ray tube face by slopingWaveforms of measured duration. This system is described in Sheftelman,US. Patent 2,766,444, wherein electronic delay lines-are used to providesequential distribution of pulses to the character wave forminggenerators which are representative of straight line increments to beformed on the tube face. Such a system requires relatively com- I plexand somewhat redundant equipment, as a plurality of encoding stages arerequired to recode the basic information to be displayed into a formsuitable for use with delay line distribution. Furthermore, manyamplifying stages must be used in connection with the delay line toequalize the amplitude of the pulse dutputs therefrom whichfurtherincreases the complexity of the required circuitry. Even withsuch complex circuitry, the characters provided are stroked fromstraight lines and lack high resolution or identification. It is,therefore, desirable to provide a relatively simplified and improvedapparatus for displaying well-defined characters at high speeds and withminimum bandwidth requirements.

Inaccordance with the invention, a generator of characters for display,such as on the face of a cathode ray device, is provided by forming atime function voltage waveform in both horizontal and vertical for theposition of all points forming a continuous trace of the outline of thesymbol or character, and applying appropriate gating waveforms to removeundesirable portions of the symbol. The electron beam of the cathode raytube or display device is, therefore, made to trace in a continuous orun- 3,417,281 Patented Dec. 17, 1968 interrupted manner thepoint-to-point segments forming the outline of a symbol, resulting inthe smooth, cursive, or continuous writing of each symbol or character.In particular, this is achieved by providing a signal line having both xand y weighting elements for each successive segment forming the symboland combining the appropriate x and y voltage waveforms to move theelectron beam cursively from point to point on the face of the tube toform the outline of the symbol. At the same time, a blanking waveformfor blanking undesirable portions of each character is provided. Theseportions or discontinuities of the resulting character are necessarilygenerated by rounding off all sharp corners in the x and y functions ofthe trace so as to reduce bandwidth requirements. This arrangement thuspermits the attainment of maximum writing rate with minimum bandwidthrequirements. For smoothness of the cursively drawn character, theinvention provides feeding the x and y outputs from the weightingelements into a filter element which smooths out steps present in theoutput of the summing network as the individual weighting elements aresequentially selected smooth, highly defined cursive character capableof being.

written at high speed.

Other objects and advantages of this invention will become apparent asthe description thereof progresses, reference being had to theaccompanying drawings, wherein:

FIG. 1 shows an exemplary symbol developed by the;

invention;

FIG. 2 is a plot of the y deflection voltage waveform;

for the cursively drawn character R of FIG. 1;

FIG. 3 is a plot of the x deflection voltage waveform for the cursivelydrawn character R of FIG. 1;

FIG. 4 is a blanking waveform adapted to remove uni desired portionsfrom the character R of FIG. 1;

FIG. 5 is a block diagram of the cursive character generator accordingto the invention; and

FIG. 6 is a block diagram of another embodiment of a cursive charactergenerator according to the invention.

Referring to FIGS. 1 to 4, there is shown a character representing theletter R which is chosen for purposes of illustration and which appearson the face of a cathode ray tube when the y voltage waveform of FIG. 2and the x voltage waveform of FIG. 3 are applied to the deflectioncircuitry of a cathode raytube. The appropriate blanking waveform ofFIG. 4 is used to blank out the undesired portions of the letter R dueto the uninterrupted travel of the electron beam. For example, the beamof a cathode ray tube, such as the electrostatic cathode ray tube shownin FIG. 5, starts its travel at the beginning of the first incrementstarting from point 0 and going to point 1 of the character R. Thismotion of the beam was the result of the vector addition of the y and 1:voltage waveforms of FIGS. 2 and :3, respectively, at the y and x platesof the cathode ray tube. The production of this waveform will bedescribed in connection with the circuitry of FIG. 5. While the spot hastravelled from point 0 to 1 of FIG. 1, it does not, however, appear onthe face of the cathode ray tube due to an appropriately timed blankingwave 60 which is applied to the'control grid of the cathode ray tube toblank out the beam from point zero to point one, although theappropriate deflection voltages are applied. At point one, the blankingwave ceases, and the visual portion of the character R appears fro-mpoint one to point nine. At point nine, the beam,

instead of being moved sharply to the right to commence the firsthorizontal leg of the character which due to the square corner wouldrequire a wide bandwith for the .r and y waveforms, is permitted tocontinue in a vertical direction with relatively no interruption throughpoints 10, 11 to point 12. While this produces a portion which isundesirable to display, it permits the generation of relatively smooth,x and y waveforms, as seen in FIGS. 2 and 3, in which the correspondingpoints show the corresponding slope of these waves. To blank out theundesirable portion of the character from points 9 to 12, acorresponding blanking wave 61 is provided which blanks out the beamduring this portion of the x and y deflection voltages. The beam is thenturned on to continue through points 12 to 26, as seen in FIGS. 2 and 3.At this point, blanking voltage 62 is applied to the control grid of thecathode ray tube and blanks out the excursion of the beam between points26 to 35, as seen in FIGS. 1 to 3. Thus, the undesirable overshoot, suchas between points 9 and 12, is also blanked out. The leg of thecharacter R is then traced on the face of the cathode ray tube byunblanking the beam from points to 39. A relatively smooth character hasthus been traced on the face of the cathode ray tube and a furtherblanking wave 63 is used to blank out the lower portion of the finalleg.

It should be understood that the same x and y deflection waveforms maybe used in connection with cursively writing the letter P except thatthe blanking voltage waveform is made to continue from point 26 to point40, thus blanking out the second leg of the letter R. By generating acharacter in this manner, high speeds can be obtained with minimumdeflection bandwidth require- 'ments. Further, the beam tracing out thecharacter produces uniform writing intensity, since the character hasbeen broken up into equal length segments during the time the characteris unblanked.

Referring to FIG. 5, there is shown a block diagram of a charactergenerating system for providing the x and y deflection waveforms and thegating waveform to be applied to the x and y plates and controlelectrode of a cathode ray device 68 of the electrostatic deflectiontype. However, it should be understood that it is not necessary to usethis type of tube, inasmuch as a magnetic deflection cathode ray tube orcombination magnetic deflection-type tube for positioning the character,and electrostatic deflection could be used for providing the display ofa character. To generate a given character, for example, the letter R, asource of sequential square waves are generated on individual outputlines by a pulse generator 70 which in this embodiment may comprise awell-known shift register, such as a series of bistable m-ultivibratorsin which a single pulse is propagated through the register to produce anoutput from each stage. It may be understood a delay line or a pulsegenerator providing sequential pulses over successive output lines maybe used. In the present embodiment, there are forty output lines 101through 140 corresponding to the forty segments of the letter R ofFIG. 1. These forty lines are fed in parallel to x weighting network 72and y weighting network 74. The signals are further fed to a blanking orgating network 76, which gates out unwanted portions of the character.In the example shown, resistor R1 in network 72 is weighted, that is,its resistance is selected at a value which, along with the weighting ofresistor R101 in network 74, provides the appropriate x and y waveformto move the beam from point zero to point one of the character "R inFIG. 1. In like manner, line 102 is fed to x resistor R2 and y resistorR102 to move the beam from position one to position two. This processcontinues until the entire character has been traced and an output fromresistors R40 and R140 has occurred. Each x and y output is combined bybeing connected in parallel and appears on output lines and 82,respectively. The currents in the individual weighting resistors areapplied through an .r-diode switching circuit 84 and a y-diode switchingcircuit 86, which are used to select one of the, for example, twenty-sixcharacters of the alphabet. An R switching signal 87 of approximatelyfour volts is applied to isolation diode 90 to gate this diode intononconduction and permit conduction of diode 91. This selection signalis also applied to the y selection circuit 86. All other gate lines areheld negative by appropriate bias, not shown. Conduction of diode 90causes diode 91 to conduct and the x waveform for the R character to beapplied to a D-C operational amplifier 94. In like manner, the Rswitching signal is applied to isolation diode 95 to cause conduction ofR diode 96 and to connect the sequential outputs of the y weightingnetwork 74 to y operational amplifier 98. It should be understood thatthe R selection gate signal is applied continuously for the entireduration of the letter R and may be provided by a source of directcurrent actuated by a mechanical or wellknown electrical'switchingarrangement, not shown. For example, the output signal of a Teletypewriter or computer could be used to actuate each of the twenty-sixcharacter lines. While no values of the Weighting resistors are givenfor matrix 72 or 74, the weighted values are generally selected to beinversely proportional to the amplitude of the particular segment to bedisplayed. For example, when weighting resistor R1 is of a value, say10,000 ohms, to produce an x component voltage for deflection from zeroto one on FIG. 1, the value of a resistor, which would deflect the beamto point 10 in the y direction, would be approximately 1,000 ohms. Thus,a complete set of x and y weighting resistors for each charactertogether with appropriate diode gating is provided. Each weightedresistor for the x and y waveforms is applied to the appropriate x and yoperational amplifiers 94 and 98, respectively, which preferably arewell-known D-C amplifiers which produce an output proportional to thevalue of the amplifier feedback resistors and 152, respectively, andinversely proportional to the value of the selected weighting resistors,according to well-known operational amplifier techniques.

It should be understood that the weighting of each resistor is selectedsuch that the beam deflects at a uniform writing rate. This is achievedby breaking the character into substantially equal segments in theregion which is to be displayed. This means the beam travelssubstantially the same distance in each of the segments and, therefore,writes at a constant speed. This arrangement achieves uniform intensityeven in non-straight portions of the trace and avoids the necessity forproviding complex intensity modulation to the cathode ray tube grid inaddition to the usual blanking wave to be described. The x and yweighting resistors are then selected at values to match the x andvoltage waveforms, shown in FIGS. 2 and 3, which, as previouslydescribed, were derived from .r and y plots of the letter R of FIG. 1.

The operational amplifiers 94 and 95, including the feedback circuitresistors 150 and 152, may be of a type commercially available, such asa model P45 operational amplifier of Philbrick Researches, Incorporated,Boston, Mass. Such amplifiers preferably provide a closed-loop bandwidthin excess of two megacycles. For example, the amplifier referenced has abandwidth capable of operation at a character rate in excess of twentymicroseconds. This bandwidth could be approximately two megacycles,while if instead of forty segments, twenty segments and a less smoothcharacter are desired, a writing speed of ten microseconds per charactermay be obtained from the same amplifier. Thus, the invention is not tobe limited to a specific bandwidth or writing speed, since individualtechniques can provide higher or lower writing speeds, although theinvention contemplates high-speed operation.

It should be understood a conventional operational amplifier may be usedwhich has a suflicient bandwidth to pass the x and y deflectionwaveforms. The output of the operational amplifier 94 is fed to ade|ay-line-typc filter for smoothing out the minute steps inherent ingenerating the individual segments making up a character. The output ofoperational-amplifiers 94 and 98 are each connected to a delay linefilter 154 and 156, respectively, which smooth the waveforms obtained atthe output of each operational amplifier by removing the tendency of thewaveforms to be stepped due to their segmentation. These x and y delaylines are of a conventional tapped type and, for example, herein consistof a plurality of serially connected LC delay sections with a tap at anappropriate number of sections to provide the desired delay-to-rise timeratio of, for example, te'n-to-one. The delay line further preferablyhas a number of sections which provide a total delay time substantiallyequal to the time taken to trace a segment on the face of the cathoderay device less one tap width. For example, a total of ten taps may beused in order to divide a given step to be smoothed into ten equalsegments, each tap being connected to the output of, for example, thethird seriesconnected LC section and to a weighting resistor. Theindividual weighting resistors which are connected to each tap are :madesubstantially equal in resistance and all are connected to a commonoutput line and fed to the input of its corresponding x and y deflectionamplifier. The delay line which may be commercially available is, forexample, a nine-tap delay line of approximately .04 microsecond per tapand a total delay of .45 microsecond, and has a typical delay-to-risetime ratio in excess of ten-toone. However, while the above delay lineprovides maximum smoothness of character, it may be omitted when a lesssmooth character can be tolerated, as cost or simplicity dictates.

Referring again to FIG. 5, delay line filter 154 is connected to aconventional x deflection amplifier 158 and delay line filter 156 isconnected to y deflection amplifier 160 and thence to x plates 162 and yplates 164, respectively, of cathode ray device 68. The x and ydeflection amplifiers are of a conventional type, capable of passing therequired bandwidth of several megacycles.

Referring now to blanking gate network 76, which is used to blank outthe undesired portions of the character R, a diode matrix is used inplace of the x and y weighting resistors. For example, a blanking waveis generated at the cathode ray tube control electrode 166 in connectionwith a conventional bias and blanking circuit 170. A blanking voltage,as seen in FIG. 4, is derived from connecting diodes in network 76 toappropriate lines 101 through 140 to receive the sequential output ofpulse generator 70. For example, a diode CR1 is connected to line 101 toprovide a blanking pulse 60, as shown in FIG. 4, which blanks out thewriting beam between point 0 and 1. In like manner, diodes CR9, CR andCR11 are connected to lines 109, 110, and 111, respectively, to produceblanking waveform 61 of FIG. 4, which blanks out the writing beamsegments 9 to 12 of FIGS. 1, 2, and 3. In like manner, the additionalblanking waveforms, shown in FIG. 4, are generated to blank out theremaining undesirable portions of the letter R. Each blanking diode inblanking network 76, upon conduction, transmits a blanking pulse throughblanking diode switching circuit 83. This circuit is similar to circuits84 and 86 in that an R gating waveform developed for the entirecharacter is applied to isolation diode 174 and to cause conduction ofdiode 175 to connect the appropriate blanking pulse into bias angblanking circuit 170. Other characters of the alphabet'are shown feedingblanking circuit 83 and are energized when the corresponding characterselection line for the x and y diode switching circuits 84 and 86 areenergized.

It should be understood that the present embodiment describes onlyalphabetical characters for the sake of simplicity. However, anycharacter or symbol desired may be generated by application of the sameWeighting and blanking techniques following segmentation of the portionof the character to be displayed into substantially equal segments. Itshould be further understood that pulse generator may be triggered atthe start of each character writing sequence or may run continuouslywith the character selection gate providing a gating pulse of fortypulse periods in duration which is applied, respectively, to thecharacter selection and blanking circuits 83, 84, and 86. While thepresent embodiment describes only alphabetical characters for the sakeof simplicity, any character desired may be generated by application ofthe same weighting and blanking technique, following segmentation of theportion of the character to be diplayed into substantially equalsegments. Also, while separate segments of a character are shownconnected to separate weighting resistors for each segment, it is alsopossible to provide a total, for example, of six weighting resistors foreach x and y network in place of forty, as shown, with a diode selectionmatrix for each character. The six resistors are then connected to acommon output lead. Each of the resistors, however, is then weighted ina binary fashion with values which represents the appropriate binarycode for the forty possible levels corresponding to the individualsegments. For example, the value of six binary resistors representbinary values 1, 2, 4, 8, 16, and 32. Thus, inorder to actuate point 35of FIG. 1, resistors representing the value of x or y can be incrementedinto sixty-four discrete steps. The binary representation of the voltagevalue of y at point 35 of FIG. 2 is generated by the appropriateselection of the correct combination of binary-weighted resistors by thediode selection matrix, to be described, for

example, in connection with FIG. 6. For example, if

point 35 has a y value of 33 volts, lines one and six of the binaryresistor network, not shown, would be actuated by way of line 135, notshown, from generator 70. Line could then be connected to two OR gate;diodes representing the value 1 and 32 of the six binary resistors. Thisprovides the correct y deflection waveform value at this particulartime. The blanking waveform,

ment for generating x and y voltage waveforms, together witha.-;bl-anking signal for cursively writing a character on the face of acathode ray tube. In particular, a-pulse? generator 200 provides asequence of signals on sixteenlines corresponding to a sixteen segmentcharacter. Lines 201 and 202 show, for example, two of these sixteenlines being fed to the character selection matrix 203. The characterselection matrix for each character contains sixteen And gatescorresponding to the sixteen lines from pulse generator-200. A selectiongate signal corresponding, for example, to the letter R on line 205 isfed to And gates 207 and 210. When the selection signal is applied toAnd gates 207 and 210, output signals are sequentially developed onlines 208 and 209 of the character selection matrix. The signal on lone205 is also applied to the remaining sixteen And gates corresponding tothe sixteen pulse lines from pulse generator 200. As shown, an outputfrom line 202 into gate 210 is provided on line 209. Appropriate codedsignals are then provided over binary lines 215 to 219 to provide abinary coded signal representing the binary value of each segment of theappropriate x waveform to move the beam of the cathode ray tube, forexample, through two segments from point zero to point two of thecharacter R in FIG. 1. In like manner, the appropriate diodes areconnected in the network to provide a coded binary signal on lines 220to 224, representing the binary value of each segment of the y waveformto move the electron beam from point zero to point two of the characterR of FIG. 1. Other diodes are connected in the character selectionmatrix to provide the remaining segments for both x and y waveforms, aswell as an appropriate blanking signal to be applied to the grid of thecathode ray tube of FIG. 1. The output of the x waveform lines is fed toa D/A converter 230 of the conventional type capable of converting thebinary signal to an analogue signal output. The y selection waveform,lines 220 to 224, are connected to the y waveform D/A converter 232,which is also of a conventional type, for appropriate generation of a ywaveform. The output of the D/A converters 230 and 232 are connected,respectively, to x and y delay line filters prior to being coupled tothe x and y deflection amplifiers, such as shown in FIG. 5. In thismanner, the character selection matrix is shown for generating anindividual character R without providing a separate weighting resistorfor each segment. In effect, the weighting is performed by applying theD/A converter with proper binary code corresponding to the desiredsignal level for each segment of the character. It is to be understoodthat additional lines corresponding to more segments than sixteen couldbe added to this ernbodiment. Also, any portion of the character may beblanked out by adding a diode line at the desired time interval whichcorresponds to the occurrence of a particv ular gate output line.

What is claimed is:

1. A generator of characters for display on the face of a cathode raytube comprising means for forming a time function waveform in bothhorizontal and vertical coordinates of segments forming a continuoustrace of the outline of the character on the face of said cathode raytube including a weighting element for each segment, means for applyingpulses sequentially to said weighting elements, means for combining theoutputs of said weighting elements to provide x and y waveforms whichmove the electron beam cursively on the face of said tube to form theoutline of said character, and means for blanking undesirable portionsof said character.

2. A character generator for display of characters on the face of acathode ray tube comprising means for forming a time function waveformin both horizontal and vertical coordinates of segments forming acontinuous trace of the outline of a character on said tube including aweighting element for each segment, means for sequentially energizingeach weighting element for each segment of the character, means forcombining the outputs of said weighting elements to provide x and ywaveforms which deflect the electron beam cursively on the face of saidtube to form the outline of said character, and means for blankingundesirable portions of said character.

3. In combination, means for forming a time function waveform in bothhorizontal and vertical for the position of all segments forming acontinuous trace of the outline of a character on the face of a cathoderay tube, said means including resistance means having a particularweighted value corresponding to each segment, means for combining theoutputs of said weighted values to provide x and waveforms to move theelectron beam cursively on the face of said tube to form the outline ofsaid character, and means for sharing the same waveform betweendifferent characters.

4. Apparatus for generating signals to deflect an electron beam to formin a cursive manner the outline of a character on a cathode ray tube,said apparatus comprising a weighting element for the values of the xand y coordinates corresponding to each segment forming the outline ofsaid character, means for sequentially applying a signal to each of saidweighting elements, and means for combining the output of said x and yWeighting elements to form x and y waveforms for moving the electronbeam of said tube in a cursive manner.

5. Deflection apparatus including a cathode ray tube for generatingsignals to deflect an electron beam through selected segments of acontinuous character to be displayed upon said tube, said apparatuscomprising means for generating an x and y waveform corresponding to thecoordinates for each of said segments forming said character, said meansincluding a plurality of gating elements for providing a coded outputsignal corresponding to the coordinates of each of said segments, andmeans for combining said output signals to provide x and y waveforms,means for filtering said waveforms, means for applying the output ofeach filter to said cathode ray tube, and means for blanking outundesirable portions of said waveforms to produce sharp corners in saidcharacter.

6. A generator of characters for display on the face of a cathode raytube comprising means for selecting x and y coordinates along theoutline of said character corresponding to segments forming a continuoustrace of the outline of the character on the face of the cathode raytube, a plurality of resistance elements, means for assigning a weightedvalue to said resistance element corresponding to each of saidcoordinates, means for applying signals sequentially to said weightedelements to provide x and y waveforms corresponding to the weightedvalues assigned, means for combining said weighted values of saidcoordinates to provide x and y waveforms which move the electron beamcursively on the face of said tube to form the outline of saidcharacter, means for individually filtering said x and y waveforms,means for applying the filtered wave-form output to said cathode raytube, and means for blanking undesirable portions of said character.

7. A generator of characters for display on the face of a cathode raytube comprising means for selecting x and y coordinates along theoutline of said character corresponding to segments forming a continuoustrace of the outline of the character on the face of the cathode raytube, a plurality of weighting elements, means for assigning a weightedvalue to said elements corresponding to each of said coordinates, meansfor applying signals sequentially to said weighted elements to provide xand y waveforms corresponding to the weighted values assigned, means forcombining said'signals to provide x and y waveforms which move theelectron beam cursively on the face of said tube to form the outline ofsaid character, and means for blanking undesirable portions of saidcharacter.

8. A generator of characters for display on therface of a cathode raytube comprising means for forming a time function waveform in bothhorizontal and vertical coordinates of equally divided segments adaptedto form a continuous trace of the outline of the character on the faceof said tube having rounded otf corners, a weighting element adapted toprovide a signal corresponding to each segment traced by said tube,means for sequentially applying signals to each of said weightingelements, means for combining the outputs of said weighting elements toprovide x and y waveforms which move the electron beam cursively on theface of said tube to form the outline of said character, means forblanking undesirable portions of said character to produce sharpcorners, and means for selecting ditferent characters.

9. A generator of characters for display on the face of a cathode raytube comprising means for forming a time function waveform in bothhorizontal and vertical coordinates of equally divided segments adaptedto form a continuous trace of the outline of the characfer on the faceof said tube, a weighting element adapted to provide a signalcorresponding to each segment traced by said tube, means forsequentially applying a signal to said weighting elements, means forcombining the outputs of said weighting elements to provide x and ywaveforms which move the electron beam cursively on the face of saidtube to form the outline of said character, and means for blankingundesirable portions of said character, said signal means includingmeans for generating digitally coded values of said coordinates.

10. In combination, a cathode ray tube having x and y deflectioncircuits, means for providing a sequence of pulses, a plurality of x andy weighting elements fed by said sequence of pulses to provide weightedoutput signals, means for selecting predetermined weighted outputsignals and applying said signals to operational amplifier means togenerate a smooth cursive x and y deflection voltage, and means forapplying said deflection voltage to the x and y deflection circuits ofsaid cathode ray tube to produce a cursive character having rounded offcorners.

11. In combination, a cathode ray tube having x and y deflectioncircuits, means for providing a sequence of pulses, a plurality of x andy weighting elements fed by said sequence of pulses to provide weightedoutput signals, means for selecting predetermined weighted outputsignals and applying said signals to operational amplifier means togenerate a smooth, cursive x and y deflection voltage, and means forblanking portions of characters on the face of said tube to producecharacters having sharp corners.

12. Electron beam controlling apparatus of the type adapted to traceselected cursive characters on the face of a cathode ray tube inresponse to x and y deflection signals comprising a plurality of gatingcircuits of the logical And type, means for feeding a sequence ofenergizing pulses to one input of said gating circuits, means forapplying a selection signal to the other input of said gating circuits,unidirectional signal conducting means connected to the output ofpredetermined gating circuits to generate coded, smooth x and ywaveforms, converter means for converting said coded x and y waveformsto x and y deflection signals, means for filtering said x and ydeflection signals, means for applying said filtered x and y deflectionsignals to said cathode ray tube, and means for blanking portions ofcharacters on the face of said tube to produce sharp corners.

13. Apparatus as in claim 12 and including means for sharing the x and ydeflection signals between different characters.

14. A symbol generator comprising a cathode ray tube, means forgenerating a plurality of pulsed signals corresponding to thecoordinates of segments of a symbol to be displayed, a deflectioncircuit for said cathode ray tube, and gating means for selectivelyapplying said pulsed signals to said deflection circuit in apredetermined pattern corresponding to the coordinates of said segmentsto deflect the electron beam of said tube in a cursive manner.

15. A symbol generator comprising a cathode ray tube, means forgenerating a plurality of pulsed signals corresponding to thecoordinates of segments of a symbol to be displayed, a deflectioncircuit for said cathode ray tube, gating means for selectively applyingsaid pulsed signals to said deflection circuit in a predeterminedpattern corresponding to the coordinates of said segments to deflect theelectron beam of said tube in a cursive manner, and means to blank outportions of said symbol from the face of said tube.

16. A generator of characters for display on the face of a cathode raytube comprising means for forming a smooth time function waveform inboth horizontal and vertical coordinates of segments forming acontinuous trace of the outline of the character on the face of saidcathode ray tube including a weighting element for each segment, meansfor applying pulses sequentially to said weighting elements, means forcombining the outputs of said weighting elements to provide x and ywaveforms which move the electron beam cursively on the face of saidtube to form the outline of said character producing rounded off cornersonly, and means for blanking undesirable portions of said character toproduce sharp corners.

References Cited UNITED STATES PATENTS 3,161,866 12/1964 Orenstein340324 3,165,729 1/1965 Richman 340-324 3,234,534 2/1966 Todman 340-324X ROBERT L. GRIFFIN, Primary Examiner.

R. K. ECKERT, JR., Assistant Examiner.

US. Cl. X.R. 340-324

1. A GENERATOR OF CHARACTERS FOR DISPLAY ON THE FACE OF A CATHODE RAYTUBE COMPRISING MEANS FOR FORMING A TIME FUNCTION WAVEFORM IN BOTHHORIZONTAL AND VERTICAL COORDINATES OF SEGMENTS FORMING A CONTINUOUSTRACE OF THE OUTLINE OF THE CHARACTER ON THE FACE OF SAID CATHODE RAYTUBE INCLUDING A WEIGHTING ELEMENT FOR EACH SEGMENT, MEANS FOR APPLYINGPULSES SEQUENTIALLY TO SAID WEIGHTING ELEMENTS, MEANS FOR COMBINING THEOUTPUTS OF SAID WEIGHT-